Gut microbiome and atherosclerosis

What is atherosclerosis?

Atherosclerosis is the build-up of fatty material called atheroma (or plaque) in your artery walls. Your arteries deliver blood from the heart to the rest of the body. As atheroma builds up, the walls of your arteries harden and narrow until blood can’t pass properly, restricting the amount of oxygen and nutrients that get to the different parts of the body.

In the UK, someone is admitted to hospital every five minutes because of a heart attack, while strokes cause around 34,000 deaths each year. Atherosclerosis plays a major role in these conditions.

Researchers are discovering that the bacteria in our gut may be used to help tackle fatty build-up in our arteries

If the atheroma breaks down, it can form a blood clot. This can block the artery and cut off the blood supply to your heart, causing a heart attack. Similarly, a stroke can happen when a blood clot blocks the artery supplying blood to the brain.

People who are known to have atherosclerosis are offered medication to lower their risk of heart attack and stroke, but there’s no treatment to reverse the process of atherosclerosis. Researchers are now discovering that the army of bacteria that lives in our gut may be used to help tackle the atheroma directly.

The gut and the arteries

Within your gut, an army of bacteria along with other microbes help break down and digest food. But it’s becoming clear that bacteria within our gut can also play a role in many conditions outside the gut, including atherosclerosis.

The amount and type of bacteria and other microbes in the gut differ from person to person and depend on many factors, including your diet. For example, people who eat a diet that’s high in sugar and fat, and low in fibre, may have different microbes in their gut to people who eat a diet that’s high in fibre and rich in unprocessed whole foods.

What’s more, the microbes may use certain foods to make chemicals that affect the rest of the body in different ways. Researchers are now interested in learning whether this process can be changed, so that the microbes produce less of the ‘bad’ and more of the ‘good’ chemicals.

The gut chemicals driving atherosclerosis

In their BHF-funded study, Dr Jonathan Shaw and his team at the University of Sheffield are changing the type of bacteria that are in the gut of mice to see how this affects the development of atherosclerosis. They hope that changing the gut bacteria could help reduce atherosclerosis and save more people from heart attacks and strokes.

“Gut bacteria produce chemicals that can be either helpful or harmful to the body,” explains Dr Shaw. “They can be helpful in producing chemicals such as vitamins that reduce inflammation, but they can also produce chemicals that lead to disease.”

“One such chemical is trimethylamine (TMA). It’s produced by the gut bacteria when we eat a diet that’s high in fat and protein. TMA has a distinct smell, sort of like rotten or decaying fish. Sometimes, this substance can end up in the breath, sweat, or urine, giving some people a unique odour after eating certain foods.”

This work will provide a basis for developing targeted therapies to accelerate the growth of ‘good’ gut bacteria

TMA is produced in the gut, where it’s absorbed into the blood, which takes it to the liver. In the liver, it’s changed into trimethylamine N-oxide (TMAO), which can be easily removed from the body by the kidneys in urine. Having a lot of TMAO in the blood has been linked to cardiovascular conditions. But how it affects atherosclerosis is still unknown. Dr Shaw and his team want to control the amount of TMA produced by gut bacteria to see how this affects the development of atherosclerosis in mice.

What to read next...